One quick nit -
Here you get more into my wheelhouse. Again, slowing your descent, or precisely slowing the lengthening of muscles, is a different sort of exercise, eccentric exercise, that also requires calories evokes a fairly big after exercise recovery response.
I do recall from my weightlifting days (20 years ago, before my joints became crunchy) that slow,deliberate negative reps (i.e. lowering the weight) were of at least as much value for building muscle mass as the positive reps (i.e. raising the weight), particularly since you could handle significantly more weight during the negative rep. We’d do a set with heavy weight until we couldn’t raise the weight anymore without assistance - and then the spotter would step in to help bring the weight up, and then we would slowly lower the weight without assistance, repeating that phase until we were physically unable to lower the weight in a controlled manner anymore.
As to whether the negative rep (i.e. movements in which the muscle is absorbing mechanical energy rather than delivering it) actually burns a significant number of calories, I have my doubts. I can trudge up a steeply inclined mountain trail at 8,000 feet with a 40-pound backpack, and my heart will pump fast, I will breathe hard and I will sweat like a pig, all indications that I’m burning calories: my cardiovascular system is struggling to deliver fuel and oxygen to my legs, and my body is doing its damndest to dump waste heat. Given that I can turn around and walk down that same trail at double the pace without sweating or breathing hard, it would seem that absorption of mechanical work does not require my muscles to burn nearly the same amount of calories.
That walk down at double the pace will also burn calories - not as many as climbing up, but not an insignificant number and more than level ground - and it will be more responsible for your being sore the next day or two. It also will raise your resting metabolic rate more over the day or so and your calories burned during subsequent submaximal exercise the next several days. The impact on how muscles respond to eccentric inclusive exercise is different than to exclusively concentric activity.
Once again, I spent last night and today thinking about the last day’s posts and what I would write next – more remarks and questions about how stair-climbing exercise works. But the recent posts by Machine Elf and DSeid have substantially written what I was going to write – in particular, about the efficiency (or lack thereof) of muscle work, and walking back down.
I was going to observe, as already noted, that after hiking up the gravity well, you don’t get any of those calories back as you hike back down. Thus, your net muscular efficiency, after hiking up and back down, is exactly 0%. (You could get energy back if, say, you climbed staircase (A) and then jumped into gondola (B) attached to rope © over pulley (D) and attached to generator (E). Generator powers grow-light (F) to grow tomatoes (G), which you (H) then eat. Allowing, admittedly, for a certain amount of inefficiency, you get at least some of your calories back.)
Oh, wait, it’s worse that that. As both DSeid and I have noted, you actually burn additonal calories walking back down. And even more than walking on level ground. With all the hiking I’ve done, I’ve certainly noticed that. So your net efficiency after hiking up and down a mountain (or staircase) is actually very negative!
I think you get more sore from the downhill hike because it exercises different muscles that don’t get as much usage in your every day walking around. As with any other exercise, if you do this a lot (as I used to do), those muscles will get into somewhat better shape too, and then the downhill jaunt won’t be sore-making so much any more. As I’ve mentioned already, you can get an even bigget dose of this by walking uphill backwards. Betcha can’t keep that up for very long at a time!
ETA: Alternate way to harness hiking energy: User (A) climbs Stairmaster (B), against resistance of eddy brake © which is rigged to generate electricity, which then powers the Straight Dope Message Board.
It’s not just different muscles, it is the nature of the eccentric contraction, that is contraction that occurs as the muscle lengthens (braking), that is most associated with the delayed onset muscle soreness (DOMS), with significant impact on strength responses, and with the delayed impact on energy used. Of course most exercise contains eccentric components but machine stair climbing (especially on the pedal style machines) is less eccentric than going both up and down real stairs. Turns out that while descending stairs (escalator!) is much less effort and energy expended during the effort, it can increase muscle strength at least as much or even more than climbing them does.
BTW as much as our bodies are far from perfect machines (and second law baby, no machine is), producing a fair amount of excess heat with exercise, walking is something we do particularly efficiently. We are relatively poor sprinters compared to other animals but endurance running and walking we do better than most.
If you haven’t been training for the activity in which you’re engaged, then yes, it’s going to make your muscles sore. One summer many years ago, I rode about 1500 miles on my bicycle, then went backpacking in the Alps. My cardiovascular system was ready, but my legs weren’t. Bicycle riding has you pedaling at high RPM but with relatively low force, whereas trudging over mountains with a heavy pack has your legs moving slowly but with much higher force. It was even worse because apparently in Europe they don’t adhere to the same trail-building standard as most US national parks do, which recommends limiting the average grade to something like 10%. The trail we were on had some ridiculously steep sustained grades, requiring far more leg force than than I was used to. On the second morning, I could barely walk on level ground. But several days later the soreness faded, and we continued walking the same sorts of trails for the next week or so without any soreness at all.
I don’t dispute that sore muscles can be inefficient, or that your body expends significant caloric output trying to repair and strengthen them after such traumatic exercise. But unless you’ve got a reliable cite for the claim that walking downhill burns more calories than walking on level ground (during the activity, I’m going to dispute that claim. I don’t recall ever being out of breath, or even breathing hard, or sweating, when walking downhill.
No doubt your legs/feet/toes move through slightly different ranges of motion when walking downhill vs. uphill, and you may get the attention of obscure muscles/fibers that weren’t really in the game before - but the muscles that are primarily responsible for extending your hip and knee joints when walking uphill - the gluteals and quadriceps, respectively - are the same ones that are primarily responsble for the braking effect (controlling extension) when walking downhill.
Try this:
[ul][li]Sit in a chair. [/li][li]Grab your quadriceps muscles with your hands; they’re the big ones just above your kneecaps.[/li][li]While you’re relaxed in the chair, feel how soft and relaxed these muscles are.[/li][li]Now slowly lean forward and lift your butt several inches off of the chair so that all your weight is on your feet. Keep your knees bent. Feel how those quads are nice and taut now?[/li][*]Now slowly squat down a couple of inches and come back up. You’ll notice (with your hands) that the quads are under constant tension the whole time, regardless of whether you’re going down or coming up. (note that the tension may vary with large movements as the geometry of the joint changes the mechanical advantage of the muscles involved.)[/ul]Notice that as long as the load is pointed in the same direction, then no matter which way the movement is - whether your knee is bending (while you squat) or straightening (coming back up) - the quads have the same tension the whole time. Same thing is happening when you’re walking, because regardless of whether you’re going uphill or downhill, gravity is trying to flex your knees and hips. Going uphill? Quads/glutes are actively pulling to extend your knees/hips. Going downhill? Quads/glutes are pulling to control the rate/amount of knee/hip extension.
Gravity is always pulling on you with the same force, whether you’re in motion (moving slowly down an escalator) or at a standstill. It doesn’t matter if the escalator is in motion or not, all the forces are the same, UNLESS the escalator is accelerating or decelerating. That is the only way thing that would make the exercise of stepping on it feel easier or more difficult.
For those that think an escalator moving the stairs down makes it easier, what happens when the escalator moves up? Would you get tired sooner walking up an escalator that is moving upwards, since you have to “overcome” more gravity? How about jumping up in an elevator that is moving upwards rapidly? That should be totally impossible right?
My google-fu is failing me right now so cites I do not got. Sorry. One NYT article that ends saying about the same walking as going downstairs, so maybe not more. (2 to 3 times more calories going up stairs than walking fast and going down stairs about a third as much as going up.)
Still some of your comments here perplex me.
You conclude from the fact that walking downhill does not make you breathe hard that it is not as calorically demanding as walking on level ground? Walking on level ground makes you breathe hard? Seriously I can walk briskly on level ground all day and literally have; walking downhill a long time OTOH is tiring. Muscle braking takes energy.
From a fitness perspective why the hyperfocus on what occurs during the exercise rather than on what the net effect is? It reminds me of the fat burning zone crud we hear about all the time (long slow aerobic burns more fat during the activity so is “better” nevermind that net fat burned over the day is greater at higher levels of intensity).
The higher impact pounding of the hitting the lower step going, btw, good for bone strength.
Finally it I am not getting a sense that you appreciate what is work from a muscle POV. The physics major would at someone holding 200 pounds balanced over his head and state that he is doing no work as he is not moving the mass (exerting force) over any distance. No distance, no work. The physiology major sees multiple muscle fibers taking turns contracting short distances, relaxing, and contracting again, all together at any time exerting enough force to keep the weight balanced.
Returning to original op here -
I can now appreciate that with the exception of changes in speed an escalator style stair climber is the same as walking up stairs. Given that those of use who do stairs however usually do not only go up, it is not the same as real stair climbing. Real stair climbing is usually an interval style activity. Supramaximal (meaning above VO2max, into anaerobic range) effort running up, eccentric activity during an active recovery phase down, repeat however many times the work-out is. Even setting up an escalator style stair machine for intervals does not replicate that.
The pedal style is not the same exercise as stair climbing even in the uphill part alone, even if the physics work (body mass lifted over a distance) was the same. This goes beyond the fact that the ascending foot is getting as much as a 25 pound push from below. In real stair climbing the top foot is pulling the body up with the help from one plyometric push off from the lower foot giving some inertia. The top foot lands on the higher step with some force (losing some energy to the step). None of that is replicated in pedal style stair stepping. Peak force productions each leg are less even if the sum total of work (moving the body mass some particular vertical distance) done is (somewhat) the same. Even if the effiiciency of work production by the muscles was the same between the two activities (which we have no reason to believe) the pattern, which muscle fibers are involved when and to what degree, is not the same.
A good exercise - no question. Demanding, yes. Uses the same large muscle groups as real stair climbing, sure. But a real simulation of how people actually do stairs as exercise? No.
Sorry if my statements were ambiguous. For clarity’s sake, I meant that walking downhill does not require significantly more caloric output than walking on level ground; it certainly does not require less. Neither one makes me breathe hard. My legs may be wobbly after descending a long steep grade with a pack on my back, but I’m not breathing hard or sweating. I’m not using more oxygen in either activity, and I’m not sweating.
Although I have some understanding of how muscles do what they do, I have been focusing on mechanical work because it has been the source of a huge degree of misunderstanding in this discussion.
You’re not comparing apples with apples here. Fitness experts have been harping on Americans to get ~20 minutes of aerobic exercise at least three times a week. The average American who finally decides to drag himself to the gym and get some exercise is not concerned with interval training, anaerobic exertion, or the “negative reps” of bounding down stairs. He just wants to engage in some cardiovascular activity like the doctor told him to so he can delay his next heart attack; he doesn’t give a rip if he’s on an exercise bike, an elliptical trainer, a rowing machine, or some kind of climber.
“The doctor said to get my heart rate up. Will this machine do it?” For him, my claims are these:
[ul][li]Working out on a stairclimber (with reciprocating pedals) may not be kinematically identical to climbing a staircase, but in terms of mechanical work and cardiovascular exertion, the difference is negligible: there is real mechanical work being done, real calories being burned, and operating a stairclimber with the pedals moving down at 1 foot per second will get your heart pumping just about as much as climbing a staircase at one vertical foot per second.[/li]
[li]Working out on a stepmill at X speed is exactly identical to climbing a staircase at X speed, provided you aren’t cheating in either case by supporting any of your weight on the handrails.[/ul][/li]
My answers aren’t particularly relevant for a fitness enthusiast who is training to win the Willis Tower Stairclimb event. For him, the details of range of motion, peak force, recruiting/strengthening those obscure muscles that assist the main workhorse leg muscles, the ability to run up stairs at anaerobic speeds and the negative reps of bounding down the stairs are all important, and neither the stairclimber or stepmill will meet his needs. For him, he’ll need a real staircase, or an escalator.
We get somewhere. Are your legs wobbly after walking that same amount of time on level ground with the same pack? I doubt it. Legs feel wobbly because the muscles are fatigued. What do you conclude?
No question that there was misunderstanding, and I readily (okay with some grumbling reluctance :)) admit that I was part of that misunderstanding. I do accept that at a constant velocity the macroscopic mechanical work of a body on an escalator style stair climber is the same as on stairs as long as the handles are not being held and that the macroscopic mechanical work performed on a pedal style stair climber is off by the amount the return pedal pushes up (apparently less than or equal to 25 pounds, which if even averaging only 15 pounds is still about 10% for our hypothetical person).
Well the op was not is it good cardiovascular activity, it was if it simulates real stairclimbing. You could say that answer is yes for the erg (the rower) as well, or the Versaclimber, if the question is only if you can get your 20 minutes of aerobic activity in on it. There are real differences between real stair climbing as exercise and the machines that limit how much they simulate the real activity.
No question that it is highly likely that the same level of rated perceived exertion will result in the same cardiovascular benefit. The same vertical feet “climbed” depends on your definition of “negligible” given that up to 25 pounds of help from below to the return foot is not so negligible, and that the kinematic differences can result in great differences of efficiency thus great differences in calories burned per vertical foot “climbed” and different effects on fitness for the same number of vertical feet (less so if people are instead working out by time at rated percieved effort or by heart rate). This part is not too dissimilar to past discussions about walking X miles or running X miles as fast as you can - in both cases the same macroscopic mechanical work has been performed, moving the mass of the body X miles but calories burned are quite different depending on the speed and net fitness impact is different yet. You cannot say that walking simulates running very well even though both are beneficial.
Again, the escalator style at constant velocity not holding handrails as the same as the portion of climbing stairs that is moving up at constant velocity not holding handrails I now get and accept.
I don’t dispute that walking downhill gives leg muscles “exercise” and may be good for muscle development and bone maintenance. I merely claim that walking downhill does not constitute aerobic exercise, at least not to any significantly greater degree than walking on level ground. If an individual wants to improve his VO[sub]2[/sub] max, he’ll need to do something that gets his heart rate up, and walking downhill ain’t gonna do it.
Let’s review the OP here:
His confusion and query were quite clearly about how using a machine on which one does not gain altitude could in any way mimic the exertion associated with an activity in which one does gain altitude. It was not about negative reps, kinematics, muscle-building, bone maintenance, or anything like that. It was a physics question, not a phys-ed question.
Senegoid can speak for himself and I may have misinterpeted but when I read “Does exercise on a StairMaster actually simulate the exercise of climbing stairs?” I understand it to be asking if exercise on a StairMaster actually simulates the exercise of climbing stairs, not just if the macroscopic physics work is the same, not whether or not the machines “could in any way mimic the exertion associated with an activity in which one does gain altitude.” Now of course some might falsely believe that the same macroscopic physics work means the same muscle work and the same fitness impact but to me the confusion (which I had) about same macroscopic physics work is only one part of the question.
But like the results one gets on both the machines and on real stairs … YMMV. 
Actually, I guess Machine Elf’s interpretation of my OP was, at first, closer to what I was explicitly asking; but his lengthy and patient explanations of the whole W = Fd stuff took the whole discussion in a direction I hadn’t even anticipated.
I had considered it obvious, a priori, that the user would have to have alternating up and down phases in the stepping cycle (Scenario B) to simulate stair climbing (at least approximately), and that the Stairmaster would need to be designed in such a way as to accomplish this. So my question, taken vary literally and narrowly was: Does it, in fact, work this way, and if so, how?
OTOH, I had assumed that the machine could, hypothetically, keep the user at a constant altitude (or nearly so) throughout the stepping cycle (Scenario A) by lowering the user at a constant and steady speed while the user raises himself at a constant and steady speed. So I assumed that it was important for the machine to NOT do this.
(Have I gotten the two scenarios labeled right this time?)
So Machine Elf caught me by surprise by arguing that it makes no difference.
So now that that is basically all settled, I’m wondering what difference it does make between the two scenarios, in terms of the “quality” of the up-stairs workout that the user gets. So this is getting into the details of the exercise physiology, which is apparently more DSeid’s bailiwick. So now I’m interested in having this discussion continue in those directions.
The notion of (vertical) acceleration and deceleration was tangentially mentioned a few times. I take this to mean the extra work of accelerating one’s body upward (in addition to the work of maintaining constant altitude) while straightening the leg. If the legs alternate the power cycles (the vertical lifting phase) with a pause between each step, you have this (vertical) starting-and-stopping pattern. If you could have perfectly continuous vertical lifting (even though alternating between left and right legs), then that starting-and-stopping doesn’t happen.
So:
(a) Is this a factor that makes Scenario B a qualitatively different exercise than Scenario A?
(b) If so, is it a significant factor (for reasonable values of “significant”; I’m taking that to mean: Significant in relation to the effort of the vertical lifting work)?
© In real life, what happens on the Stairmaster?
We’ve established that Scenario A (continuous motion with constant-altitude CoG) could happen in two ways: With high-resistance setting, it happens slowly, with the user walking and lifting himself very slowly; or with low-resistance setting, in which the user has to trot much quicker to keep up. I’m still a little skeptical as to whether either of these scenarios actually does happen in real life; and if either does, to what extent it is similar to stationary stair-case climbing? And we’ve established that slow-motion weight lifting is qualitatively different than fast-motion weight lifting.
So, having settled that the W=Fd is the same for both, I’m interested in DSeid’s discussions of what other matters come into play in exercise physiology, and how much those to affect my question: How closely does the Stairmaster simulate actual stair climbing?
I get that the Stairmaster is one-way only and completely omits the entire exercise of walking back down all those stairs. (Or can the machine also be used in a down-stairs mode of operation?)
Well I linked early on to one motion study of how a stairmaster was used vs real stair climbing. A very limited study looking at one person so take of it what you will.
From a practical POV the biggest difference likely is that it is very hard to cheat on real stairs, whereas proper technique is essential to get the fullest possible work out on a machine.
That said if one’s sole purpose is to get an aerobic workout and one gives an honest effort sufficient to reach the same rating of percieved effort or same heart rate for the same period of time the exact muscle patterns and efficiency of converting that muscle and aerobic effort into macroscopic physics work are not too important.
Unfortunately, it’s all a bit academic for me now, but this is an interesting discussion.
I lived for many years in places where there were mountains nearby with extensive and well-established hiking trails. That’s what I did. Anybody know about Big Basic State Park and the Skyline-to-the-Sea Trail? I hiked that entire trail (about 30+ miles), in little pieces, over a period of about a year, circa 1986. I also lived and hiked a lot in San Luis Obispo County.
Now, I live in a place that is about as flat as Kansas for long distances all around. I have to drive about two hours to get to any place where there’s good hiking. Or I could drive downtown, where there’s a five-level parking structure. I could hike up and down the stairs there, maybe. But that’s just toooooooo boring. I can’t really afford to join a gym; which would also bore me to death.
So, like I said, it’s academic for me. But I’ve learned a lot here.
You don’t need five levels to do stairs. And the thing about stairs in your own home, like from your basement, is that you can mix it up, carrying various amounts of weights up and down, carefully taking backward steps down, running up two steps at a time …
Late to the game. Reviving this thread for a couple of tangential points.
Now you’re talking about something I can really speak to. The C.O.L.B.E.R.T. (called T2 in the business) isn’t the first treadmill on ISS, or even the first US treadmill. The Russians had a treadmill called BD-1 from MIR, but it wasn’t very good. The US flew a design called TVIS, and installed it in the Russian Service Module. A decade later, the US started looking at a new design. They wanted something based more on a commercial treadmill system than a unique custom design. They came up with T2, and flew it and installed it in the US segment. But the Russians kept TVIS in service while they worked on a new design of their own. Eventually, they flew and installed BD-2 in the Service Module, and deorbited TVIS.
As shown in the link, users of treadmills in space have to use some sort of cable system to apply loads. TVIS used a motorized spring system (using garage door springs) to have adjustable loads applied to a harness similar to the one shown. Except that harness is much better. The bungees shown were originally designed for use with TVIS, and carried over to the T2 use. They are an alternate way to load. They use rubber surgical tubing as a bungee in cloth sleeves, where load is based upon extension of the bungees. The addition of clips gives the ability to adjust the load value for each user to match their height and the doctors’ recommended loading.
Correct. The harness and loading system replaces gravity.
This is correct. It is one of the reasons a treadmill is so important in space. It provides the impacts that resistive “weight lifting” and cycle riding can’t.